A variety of approaches are used to reduce energy consumption in buildings. Among the approaches being considered and applied is the more efficient use of sunlight to provide lighting inside buildings. One technique for supplying light inside of buildings, such as in offices, etc. is the redirection of incoming sunlight. Because sunlight enters windows at a downward angle, much of this light is not useful in illuminating a room. However, if the incoming downward light rays can be redirected upward such that they strike the ceiling, the light can be more usefully employed in lighting the room.
A variety of articles have been developed to redirect sunlight to provide illumination within rooms. A light deflecting panel is described in U.S. Pat. No. 4,989,952 (Edmonds). These panels are prepared by making a series of parallel cuts in sheets of transparent solid material with a laser cutting tool. Examples of daylighting films include European Patent No. EP 0753121 and U.S. Pat. No. 6,616,285 (both to Milner) which describe optical components that include an optically transparent body with a plurality of cavities. Another daylighting film is described in U.S. Pat. No. 4,557,565 (Ruck et al.), which describes a light deflecting panel or plate which is formed of a plurality of parallel identically spaced apart triangular ribs on one face. Examples of films that have a plurality of prism structures are described in US Patent Publication No. 2008/0291541 (Padiyath et al.), and pending US patent application Ser. No. 61/287,360, titled “Light Redirecting Constructions” filed Dec. 17, 2009 (Padiyath et al.), and Ser. No. 61/287,354, titled “Light Redirecting Film Laminate” filed Dec. 17, 2009 (Padiyath et al.). Constructions that incorporate both light redirection and light diffusion include the pending U.S. Patent Application Ser. No. 61/469,147, titled “Hybrid Light Redirecting And Light Diffusing Constructions” filed Mar. 30, 2011 (Padiyath et al.), and Canadian Patent Publication No. 2,598,729 (McIntyre et al.).